Regarding demand for glow plugs used to preheat diesel engines, recently, there has been increasing demand for glow plugs capable of quickly raising temperature. Glow plugs are required to exhibit, for example, such a temperature rise performance as to reach 1,000° C. in about two to three seconds at an applied voltage of 11 V. In order to satisfy such a requirement, in Patent Documents 1 to 3, for example, a silicon-nitride-tungsten-carbide composite sintered body, which is a conductive ceramic, is used to form a heat-generating resistor whose end portion (heat-generating portion) exhibits high resistance and whose lead portions exhibit low resistance.
Patent Document 1: Japanese Patent Application Laid-Open (kokai) No. 2002-203665
Patent Document 2: Japanese Patent Application Laid-Open (kokai) No. 2002-220285
Patent Document 3: Japanese Patent Application Laid-Open (kokai) No. 2002-289327